Recently, according to popularization of electric cars, simple and more convenient charging methods are being required, and safe and rapid charging methods are being developed. In addition, various non-contact wireless charging methods are proposed which may address inconvenience of a wired charging method for charging by plugging in an electric car.
For electric car charging, non-contact charging methods, which perform wireless charging in a short range by using a magnetic induction method and a resonant magnetic coupling method, are at the commercialization stage. Typically, non-contact charging of an electric car is performed by mounting one reception pad, which receives wireless power, in the bottom part of the electric car and installing one transmission pad, which corresponds to the reception pad, at a specific position in a parking zone. Since such a typical wireless charging method has a low transmission efficiency (e.g. 70 to 90%) and charging takes a longer time than wired charging, the transmission pad is mostly installed in a dedicated parking lot and charging is performed at night.
The magnetic induction method uses an electromagnetic induction principle that when a magnetic field is generated at a wireless power transmission coil, electricity is induced at a reception coil due to an effect of the magnetic field. The magnetic induction method is advantageous in that the transmission efficiency is very high, but has a limitation in that the transmission efficiency rapidly decreases, when a transmission coil is separated from a reception coil by several centimeters, or centers of the coils do not match. It is a magnetic field resonance method that compensates for such a limitation. In the magnetic field resonance method, a wireless transmission/reception distance is elongated and the transmission efficiency is improved by adding a resonance function to the transmission and reception coils.
Unlike the magnetic induction method, the resonant magnetic coupling method is advantageous in that wireless power transmission/reception is possible with high efficiency even in a far off place, but has a limitation in that the transmission efficiency becomes lowered by influences of an installation position of a transmission/reception module, a change in operation state, or surrounding conductors in an environment where charging is actually performed. The performance thereof is gradually improved. The magnetic induction method also generates an electromagnetic wave higher than a regulation level of each country in a place where a magnetic field is concentrated near the transmission/reception coil.
Radio frequency identification (RFID) is technology for recognizing information in the distance by using a radio wave. RFID, which includes an antenna and an integrated circuit, records information in the integrated circuit and transmits the information to a reader through the antenna. The information is used for identifying a subject to which the RFID is attached. Since the RFID reader communicates information with the RFID through a radio wave, it may read the RFID in a long distance as well as in a short distance and also receive information through an object disposed therebeween.
For reference, the related patent literature is PCT publication No. WO 2011/049352.